Wran began his political career in 1970 when he became a member of the upper house of the Parliament of New South Wales, the Legislative Council. Three years afterwards, he moved to the lower house, the Legislative Assembly, in the seat of Bass Hill. Support for this move had been organised by the General Secretary of the FMWU, Ray Gietzelt.[5] He then challenged Pat Hills for the state leadership of the ALP (which Hills had held since 1968). In this challenge he had cross-faction support from right-wing powerbroker John Ducker and left-winger Jack Ferguson. There were two rounds to the leadership vote which resulted in a tie between Hills and Wran in the second ballot. However it was ruled that in the event of a tie in the second ballot, the candidate who won the most votes in the first ballot would be the winner. Since Wran had won one vote more than Hills in the first ballot, Wran was therefore declared the new leader.

In May 1976, six months after Gough Whitlam's federal ALP government's dismissal, Wran led Labor to victory, narrowly defeating the Liberal Party premier, Sir Eric Willis. Wran's win was not assured until it became clear that Gosford and Hurstville had fallen to Labor by only 74 and 44 votes respectively, giving Wran a one-seat majority. In 1978, campaigning with the slogan "Wran's our Man", his government won a 13-seat swing on the back of the largest primary vote for any party in a century, popularly known as the "Wranslide". The Opposition Leader on that occasion, Peter Coleman, lost his seat. In 1981, Wran won a second "Wranslide", picking up six seats for what is still Labor's largest proportion of seats in Parliament. The Opposition Leader, Bruce McDonald, failed to be elected to the seat that he contested, marking the second time in a row that an Opposition Leader had failed to be elected to Parliament. Labor also reduced the Liberals to 14 seats, the same as its nominal junior partner, the National Country Party. He won a fourth term in 1984; although he suffered an 11-seat swing, he still won a larger majority than any of the victories won by the Liberals' Sir Robert Askin in the 1960s and 1970s.

In 1977, Wran supported Al Grassby, former Federal Immigration Minister, in allowing Domenico Barbaro, a Mafia figure in the Griffith region of New South Wales, back into Australia after having been earlier deported because of his criminal record.[6] However, as journalist David Hickie explains, Wran attempted to undermine the influence of organised crime, particularly in the area of illegal casinos.[7]

Wran was also very popular, at one stage rating over 80 per cent approval in opinion polls. He was often talked about as a national political leader and rated highly in national polls as an alternative Labor Leader to Bill Hayden. He featured in Hayden's 1980 federal election campaign, along with Bob Hawke.

Wran's childhood home in the Sydney suburb of Balmain

Wran was a Labor premier at a time when most Australian governments were held by conservative coalitions. During his 10 years as Premier of New South Wales, the government embarked on a program of reform and change. Priorities were public transport (with the exception of the Warringah Transport Corridor which was cancelled despite a recommendation by Justice Michael Kirby that it be built), the environment, consumer protection and job creation. He also achieved significant electoral institutional reform such as a democratic Legislative Council, four-year terms, public funding and disclosure laws and a pecuniary interests register for members of parliament. He called on Edwin Lusher, firstly while a QC and then as a Judge of the Supreme Court of New South Wales, to chair commissions of inquiry into police administration and gambling.[8] He also undertook the state's largest capital works program and refurbished many iconic places in Sydney. His government also built the modern-day Darling Harbour precinct.

In 1983, Wran faced the StreetRoyal Commission over claims by the Australian Broadcasting Corporation (ABC) current affairs show Four Corners that he had tried to influence the magistracy over the 1977 committal of Kevin Humphreys, who had been charged with misappropriation of funds.[9] His Corrective Services Minister, Rex Jackson, was jailed in 1987 for accepting bribes for the early release of prisoners.

Wran resigned both the premiership and his seat in Parliament on 4 July 1986, after continuously holding office longer than any other premier in the history of New South Wales until that time. Bob Carr has since broken that record. (Henry Parkes served longer than either Wran or Carr in total, serving five terms between 1872 and 1891.) The by-election for Wran's seat of Bass Hill was narrowly won by Michael Owen for the Liberal Party. Wran is remembered by the phrase "Balmain boys don't cry".

Wran's first marriage was in 1946 at the age of 20, to Marcia Oliver, a showgirl at the New Tivoli Theatre.[1] Oliver had a young son, who Wran adopted, and they had two other children. In 1976, a month after his divorce was finalised and three months after becoming Premier of New South Wales, Wran married Jill Hickson,[10] and they had two children together. Wran and Hickson separated several times, first briefly in 2006, then in August 2011 after Hickson said she had been "frozen out" of her husband's personal affairs by his daughter Kim and his friend and business partner Malcolm Turnbull.[11] They had reconciled by December 2011.

A severe throat infection in 1980 required injections of teflon to strengthen his damaged vocal cords, resulting in his characteristic croaky voice.[12]

In his later years, Wran had dementia and since July 2012 had been under special care in Lulworth House aged care facility in Elizabeth Bay.[13] He died there on 20 April 2014 at the age of 87. He was survived by his wife Jill and five children.[14]